RE: Tyrannosaurus third finger

["Thomas R. Holtz, Jr." <tholtz@geol.umd.edu>]

> From: owner-dinosaur@usc.edu [mailto:owner-dinosaur@usc.edu]On Behalf Of
> Dino Guy Ralph
>
> Donna:
>
> I brought this up before.  The verdict from the Theropod -- oops! -- I mean
> the Dinosaur Mailing List was that Rexy had a third metacarpal, but not a
> third finger, making it difficult to determine whether it was making rude
> gestures.  (Okay, I made up that last comment myself).
>
Quite so!

Yes, "Peck's Rex" has the third metacarpal preserved, as do several other 
specimens (but not published). I've even seen isolated T.
rex mcIIIs in collections as bone indet.

The metacarpal was without phalanges.

Incidentally, the metacarpal of T. rex is distinct from the extremely reduced 
form in Tarbosaurus, and from the slender rod-shaped
form in albertosaurines and Daspletosaurus.

> On the other hand, the Early Cretaceous Chinese basal feathered
> tyrannosauroid, _Dilong paradoxus_, did have three fingers, but it's the
> only tyrannosauroid yet discovered with three manual phalanges, and it
> predates _T. rex_ by about 60 million years.

Eotyrannus seems to have had a perfectly good tridactyl hand, too.


                Thomas R. Holtz, Jr.
                Vertebrate Paleontologist
Department of Geology           Director, Earth, Life & Time Program
University of Maryland          College Park Scholars
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                Building 237, Room 1117
                College Park, MD  20742

http://www.geol.umd.edu/~tholtz/
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